(a) Field of the Invention
The present invention relates to a multilayer structure which may be suitably used in packaging industry, particularly for production of containers, and to an easily openable container and an easily openable lid produced by using the multilayer structure, which due to their excellent sealing property and openability, may be suitably used for storage or packaging of foodstuffs, medicines, cosmetics, and the like.
(b) Description of the Related Art
When packaging articles, particularly when packaging foodstuffs, boiling or retorting has been conducted to sterilize the articles after they are filled in containers. At the time of boiling or retorting, the containers cannot withstand the interior pressure without increasing the sealing strength between the container body and the lid member, while an increased sealing strength causes the decrease of openability when the container is opened for using the content. In Japanese Patent Application Laid-open No. 62-251363, disclosed is an easily openable container excelling in both sealing property and easy openability, wherein the above problems are solved by a particular technique. That is, in this technique, opening the container at the time of use is not conducted by general peeling of the sealed portion, but a multilayer container is used as the container body to utilize an interface between its layers as the open plane to be peeled for opening the sealed container, and the inner surface layer is provided with a notch at a periphery inner to the sealed portion so that the lid member is peeled off together with the inner surface layer, and the multilayer container inside the notch will remain as it is without peeling off its inner surface layer.
However, the container also has a problem in that it is difficult to uniformly control the peeling strength of the layer to be peeled off and, therefore, stable openability cannot be obtained.